1. Field
Disclosed herein is a collapsible radial or cross-ply tire, to a method of collapsing and to a use thereof on a passenger vehicle.
2. Description of Related Art
In what follows:                a “circumferential plane” means a plane perpendicular to the axis of rotation of the tire,        an “equatorial plane” means a circumferential plane passing through the middle of the tread surface of the tire, and        a “radial plane” means a plane containing the axis of rotation of the tire,        an “axial direction” means a direction parallel to the axis of rotation of the tire,        a “radial direction” means a direction intersecting the axis of rotation of the tire and perpendicular thereto,        a “circumferential direction” means a direction tangential to the surface of the tread in the direction of rotation of the tire,        “radially on the inside of” means closer to the axis of rotation of the tire,        “radially on the outside of” means further from the axis of rotation of the tire,        “axially on the inside of” means closer to the equatorial plane,        “axially on the outside of” means further away from the equatorial plane.        
A tire comprises a tread intended to come into contact with the ground via a tread surface, extending radially towards the inside in the form of two sidewalls connected to two beads intended to provide the connection between the tire and a rim.
A radial tire more particularly comprises a reinforcing structure comprising a crown reinforcement, radially on the inside of the tread, and a radial carcass reinforcement, radially on the inside of the crown reinforcement.
A cross ply tire differs from a tire built with radial tire technology in that there are at least two crossed carcass plies making angles other than 90° with respect to the circumferential direction of the tire. The plies are said to be “crossed” because the angles are of opposite sign from one ply to the other.
The carcass reinforcement usually comprises at least one pair of reinforcing elements which consists of threads substantially parallel to one another and usually making, with the circumferential direction, an angle comprised between 85° and 95°. The carcass reinforcement is, in most tires, and in each bead, wound from the inside towards the outside of the tire around a circumferential reinforcing element called a bead wire to form a turn-up. The bead wire may be formed of an assembly of elementary threads or of cords, themselves formed of an assembly of elementary threads.
The crown reinforcement generally comprises several crown reinforcement layers. These layers most often consist of metal reinforcing elements embedded in an elastomeric material.
In the case of a tire for a passenger vehicle, the thickness of the crown reinforcement, which essentially consists of the radial stack of the crown reinforcement and of the carcass reinforcement, is usually comprised between 2 and 7 mm. A sidewall of a tire for a passenger vehicle generally has a thickness comprised between 2.6 and 7 mm.
A collapsible tire for a bicycle, comprising a carcass reinforcement each end of which is anchored in two beads by being turned up around a reinforcing element called a bead wire is already known from document WO 10/100088. Each bead is extended radially by sidewalls which join to a tread. This tire comprises a bead wire formed by winding a saturated and unwrapped metal cord formed of filaments.
A collapsible tire mounted on a rim, for vehicles such as motor vehicles, is also known, from document FR 2 348 065. This tire comprises a substantially annular tread situated centrally, and sidewalls which extend the tread and end in inextensible beads, which means beads the bead wire of which has a high level of circumferential rigidity. When the tire is deflated, the sidewalls can be bent inwards towards one another so as to be practically flattened inside the tire in relation to the tread.
Finally, document U.S. Pat. No. 4,057,091 also discloses the collapsing of a tire for a motor vehicle when it is mounted on a rim. In such a combination and when deflated, the tire can be flattened by folding its sidewalls in on themselves towards this rim.
However, such tire collapsing configurations for motor vehicles assume the rim still to be present, and still occupy a great deal of space and exhibit a high weight due to the presence of the rim.
Moreover, when the tires are manufactured at production sites distant from the sales sites it is necessary to transport them. When they are being transported, even if compressed together, the tires still occupy a substantial volume.
Specifically, one mode of packaging currently employed is first of all to lay a first row of tires vertically and in a line to make an angle of inclination with the ground so that they are partially superposed. Other tires are then incorporated and pushed into that part of the hole of each tire of the first row that has been left free, thus forming a second row. Such a mode of packaging allows 30% more tires to be packed in per m3 by comparison with a layout in which the tires are placed side by side without deformation.
Hence, a need to be able to package one or more tires for a motor vehicle, not mounted on rims, in a more or less compact manner for the time they spend in transport and/or in storage, and without damaging their internal structure while at the same time allowing them to revert very quickly back to their initial shape when they are no longer collapsed still remains.